The present disclosure is generally directed to media streams in the area of communications and more specifically in the area of voice over internet protocol (VOIP).
In VOIP systems, a voice call may be setup by a central call control providing centrally generated media streams and dial tones from a central media gateway. Once the call is established, the control of the media stream as well as the path of the media stream between caller and callee is usually transferred to a decentralized configuration. Transferring the media stream to a decentralized configuration releases the media gateway. The switching from centralized to decentralized media streams can result in audible clipping when the talk path between the caller and the callee is broken for a short period of time. The primary cause of the clipping is that the media stream (RTP stream) of the media gateway (e.g., VoIPBoard in the media gateway) is stopped and the caller's phone sends its media stream directly to the callee's phone (otherwise known as switch over) and vice versa. For that reason the jitter buffers of both phones have to be re-synchronized, which may result in audible clipping and be offensive to the listener or viewer.
The lack of synchronization is due to a difference in timing of packets received by a node (e.g., a caller phone, a callee phone, a media gateway) as a result of network latency variation, network congestion, timing drift, packet route changes and media gateway processing delays. The lack of synchronization between an incoming centralized and decentralized media stream results in anomalous data on switch over. The anomalous data may cause aspects of a spoken conversation to be lost during this switch over, and therefore, portions of a conversation may need to be repeated.
Some current systems avoid the clipping during switch over by using decentralized media streams from the beginning. This, however, presents other problems as dial tones from the media gateway can then no longer be used, meaning each IP telephone must support local tones. If announcements have to be played (e.g., from the local carrier) this workaround will fail, and thus a central media gateway must be used.
Certain embodiments of the present disclosure address these and other problems.